A canister comprising first to third chambers in which an adsorbent material such as activated carbon is disposed is known. The first chamber is provided with an inflow port connected to a fuel tank and an outflow port connected to an internal combustion engine. Fuel vapor flowing in from the inflow port is adsorbed on adsorbent materials in the respective chambers. The third chamber is provided with an atmosphere port. At the time of purging, air (hereinafter referred to as “purge air”) flows in from the external of a vehicle via the atmosphere port. The fuel adsorbed on the adsorbent materials in the respective chambers is removed by the purge air, and flows out from the outflow port toward the internal combustion engine.
Patent Document 1 describes that activated carbon having high performance of desorbing the adsorbed fuel (hereinafter referred to as “low adsorptive carbon”) is disposed in a third chamber of a canister. This enables sufficient removal of the fuel adsorbed on the activated carbon in the third chamber even when the amount of purge air is small at the time of purging.
On the other hand, Patent Document 2 describes that activated carbon having a large adsorption capacity (hereinafter referred to as “highly adsorptive carbon”) is disposed in a third chamber of a canister. This can suppress migration which is a phenomenon that the fuel accumulated inside moves toward an atmosphere port and flows out from the atmosphere port when the canister is left as it is over a long term.